Process of calcining limestone.



R. HART. PROCESS 0F cALclNmG LiMEsoNE.

APPLICATION FILED FEBi 17, 1916.

Patented Apr, 11, l1916.

Flc; 1.

REA HART, 0F ROCKFORD, ILLINOIS, ASSIGNOR T0 REA HART AND BAILEY B. PAGE, COPARTNERS DOING BUSINESS AS HART & PAGE, OF'ROCKFORD, ILLINOIS.

Specification of Letters Patent.4

Patented Apr. 11, 1916.

Continuation in part of application Serial No.1`20,146, led April 9, 1915. This application filed February .17, 1916. Serial No. 78,892.

To all whom t mcg/ concern Be it known `that I, REA HART, a citizen of the United States, residing at Rockford,

in the. county of Winnebago and State ofA Illinois, have invented a ,certain new and useful Process. of Calcining Limestone, of which the following is a specification.

This application is a continuation in part of. my copending application Serial No.' 20,146,1i1ednpri1 9, 1915.

. To obtain a high-grade product, the calcination of the limestone must be controlled and varied with due re ard to the character of the stone. tially pure calcium carbonate, the process of calcimng the stone is simple and safe, as

there is no danger of overburning. `If the limestone contains a greater or less amount of magnesia, the .calcination of the limestone requires'carefl control in order that the limestone shall not be overburned.-

- Because of its abundance and cheapness, wood has, in the past, been used almostum'- versally as fuel in burning limestone. lWhile many efforts have been made to use coal and .producer gasin themanufacture of lime,

wood has remained the favorite notwithstanding it's"rapidly increasing cost and growing scar'city, for the reason that` whenwood is used as the fuel there is little or no danger ofoverburning the limestone, where- -as coal and producer. gas as heretofore applied have not been suiciently controllable to prevent overburning. of magnesia'nwlimestone. v

The object of'this invention 'is -to provide a process whereby as maybe practically lused in the productlonof Ahigh-grade lime,

even where the limestone contains consid# erable amounts of magnesia." The processconsists in calcinn .the stone with ajcomb ustible gas whic has been so greatly .diluted with steam -that a very longand comparatively cool flame is produced, simu-` lating in its effects the flame produced in the burning of woodin Aa lime kiln.

The nature of the invention will bemore fully understood from a consideration of the following description and the accompanying drawings, in Awhich drawings-'v Figure 1 is a v iew (more or,less diagrammatic) illustrating an apparatus which may Ifvthe limestone be substan;

be used in practising lmy invention. Fig. 2 is a vertical central sectional view through the lime kiln, taken in the plane of 4dotted line 2 of Fig. l. Fig. 3 is a fragmental horizontal sectional view taken intheplane of ln the drawings, 1 denotes a kiln of'corn` v mon construction, said kiln comprising the hoppery2, the central shaft'. 3, the cooler 4, the drawoff opening '5 and two oppositely arranged combustion chambers 6.

7 are the furnacefdoors, Sthe grates, 9 the ashpit,.10 the ashpit door, and 11 (Fig. 3)

openings communicatingbetween the combustion chambers and the shaft. The kiln is open at its top in order that the carbon dioxid may escape freely andrapidly.'

The gas to be burned inthe chambers 6 may be produced ina gas roducer A of lan'y suitable character. shown a* gas producer comprising a grate 12,v a chamber413 to contain a bed offuel of suitable "depth, a charging hopper 14, poke holes 15, and an ashpit. 16. Air under pressure is supplied to the fuel bymeans of a` fan or blower 17 of any suitable type. Y. The outlet of the fanorblower is connected by erein I have a pipe.\18 to an annular air-heating chamberl 19 contained within the walls of thegas pro-v ducer,said,chambe r communicating with the space below the grate-12 through a passage 20.

Steam is supplied under pressure tothe The moisture also assists in the liberation of carbon. dioxid from the stone.

I have found it desirable to supply sui cient steam through the pipe 23 so that a very wet producer gas is obtained of the Mond type. As .the process has been prac# tised by me,l sufficient steam is admitted through the pipe 23 so that the gaseous mixture leaving the gas producer contains on the average about 14% 'of steam by volume.

rlShe gas produced in the chamber 13 may be conducted to the lkiln in any suitable manner, as by means -of conduits 24 and pipes 25. As shown in my said application Serial No. 20,146,'a conduit 24 and a pipe 25 may be provided for each furnace,- each pipe 25 extending to a point in front of one of the furnaces of the kiln.

The valve-by means of which the supply of gas to the burner is controlled, may be of any suitable construction, that herein shown consisting of a circular valve member 38.

The burner 36 may be of any preferred construction. It projects through an opening in the furnace door 7 and' extends to a suitable point withinthe combustion chamber 6. Preferably the burner is of such size as to produce a large flame. A burner` of eight-inch diameter, in connection with a kiln of dimensions given has given good results. The shape of the orifice is such that the gas leaves the burner under relatively small pressure.

The size of the burner and its location within the combustion chamber depend upon the size of the furnace andperhaps other factors. rl`he burner should be far enough away from the openings l1 so that the flame may ,Spread out and not be concentrated upon a relatively small part of -the charge,- as such a concentrated flame tends to overheat and discolor the lime.

As hereinbefore stated, the gaseous mixture leaving the producer A contains a relatively large percentage of steam. Still further to dilute the mixture l provide a pipe 37 communicating with the boiler 22 and arranged tol discharge steam into the burner practised by me, sufiicientsteam is admitted through the pipe 37 to bring the total amount of steam in the hot combustible mixture supplied to the burner 'up to an average of about 30% by volume.

The percentage of steam in the combustilble mixture' supplied to the burners will vary slightly at times, due to variations in operatlng conditions. lf desired, substan- 'tially all of the steam might be supplied Lafraise kiln) being effected by adjusting the How of steam through the pipe 37 bymeans of a valve 37a.

Airto support combustion entersthe kiln through the draw-0H opening 5 and also through the ashpits 9. In practice, it often happens that the doors 7 or the `frames upon which they are hung do not fit tightly, so that more or less air enters through the front end of the combustion chamber.

In practice, the supply of air and steam to the gas producer is regulated in accordance with vthe `particular material being burned. ln calcining limestone containing magnesia, I prefer to use a relatively cool ame rolling up from the burner and spreading out within the combustion chamber, and thence passing through the spaces 11 and upwardly within theshaft 3.

rlhe gas discharged from the burner takes air for combustion from the space surrounding the burner, mixing slowly with this air by reason of the velocity of the gas and the draft through the kiln, the result being that a long flame is produced. The large amount of steam flowing with the gas passes into the combustion zone and reduces the temperature there vbyk reason of its high specific `heat and decomposition into its elements.

By volume. C02 .091 C() .056 (1l-ll,i l .042 H24. .126 N2-; .385 20 .300

Percentages by vvolume have been stated on the basis of the space each constituent of the mixture wouldl occupy separately at the same pressure and temperature.

llt has been proposed to slightly dilute -producer gas with carbon dioxid drawn from the shaft, but this has not proved successful, for the reason that the carbon dioxid reunites with the lime or partially calcined stone, the quality of the product being thereby impaired, and for the urther reason that the producer gas is not suciently diluted.

By means of the valves 38 the amount of gas supplied to the kiln furnaces may be regulated in the manner necessary to heat the lkiln uniformly, notwithstanding the direction of the wind, peculiarities in the construction of the particular kiln,V and other `factors tending to prevent uniform distribution of the heat.

e lt willbe seen that no attempt ismade to OCD lll@

iis

remove the tar and other heavy products '.prising producing a Wet combustible gas,

nnxlng steam with said gas, and burning a charge Aofy limestone. v l

2. The process of'calcining limestone comprising producing a -Wet combustible gas,

mixing sufficient steam v viththe gas tomake the total amount vof steam approximately 30% by volume2 and burning the combined 15 steam and` gas 1n contact with a charge of limestone.

' 3.. The process of-calcinnglime'stone comprising first obtaining a wet producer gas ofthe Mond type, mlxing steam with said 20 gas, and burning'i the combined steam and gas in Contact with a charge 'of limestone. the combined steam -and gas in contact with In testimony whereof, I hereunto set my 1 REA HART. In-the presence of HARRY BQ NORTH, ARTHUR .E. FISHER. 

